parking assist system

So, last year, my parking assist was flaky. Screen would pop up for a second or two, system would beep, then nothing.

Scan showed:

Parking sensors: 01546 - Sensor for PDC Rear Left Middle (G204). At one point, I put my ear near it and didn't hear the "tick, tick, tick" but I could hear the other sensors. I bought a sensor online but put off swapping because it's a pain to get too the rears. Then, if fixed itself when it got cold in Michigan.

It's been working all winter till recently.

Since it seems temperature sensitive, I'm wondering it it's a connector loose or a controller issue. First, where is the control module?. Next, is thee any way I can get my hand near the connector on the sensor itself with pulling the bumper skin off?

this afternoon, I got down there and unscewed the 4 or 5 screws on the plastic part of the bumber valence. I was able to bend it down and reach the left middle sensor which the scan tells me is not working. I remember a while back asking my grandson to put his ear next to the sensors and the left middle was the only he couldn't hear ticking. I tried to listen today but even with my hearing aids turned up, I didn't hear it.

Although I could reach it with one hand, I couldn't pull the connector off. I did buy a sensor and it's sitting here on my desk. What I'm wondering is if one sensor craps out, does it prevent the system from working altogether? The screen pops up, show the image of the car for a second of two, beeps, then nothing. Perhaps it's a safety thing if one sensor is out, it figures you shouldn't rely on it, especially if a kid is standing there and you might run over him.

Mine is 2004 it had the beeping thing only if one sensor went bad the system would not work. Since upgrading the control module to newer versions now if one sensor or more don't work the system still works with the working sensors i just don't get any warning on the bad sensors.

I just replaced one of these sensors in my 2007 S6. I would get a long beep every time I put the car in reverse, then nothing. VCDS said it was the right middle sensor - I never did listen to see if it was ticking or not. In this car the rear sensors are wired in series, so if one goes out, the whole system won't work, even if the others are OK. Sounds like a newer control module operates differently. In any case I ordered 4 sensor from ebay for about $20, but put off the repair for the same reasons you did. Finally, a couple of weeks ago I decided to do it. I put the rear up on jacks, unscrewed that valance and wiggled my arms up in there, and was able to remove the sensor from the rear bumper, unplug the bad sensor (requires two hands up there, and having the car on jacks helped) and put a new one in. Altogether about an hour. I put on a long sleeve shirt and wedged a piece of wood in there to keep the valance and bumper cover apart while I worked. System works great now and I have 3 spare sensors for when the others go out.